我已经阅读了很多关于如何使用Parcel的文章,我已经在我的应用程序中使用过它,但它无效。我刚刚创建了一个活动,您可以使用Sockets
连接到计算机。我在Socket的java.io.PrintWriter
上打开了一个OutputStream
,我希望有另一个活动(在第一个活动中触摸按钮时打开)使用同样的PrintWriter
。我认为我在这里犯的错误是没有克隆PrintWriter object
。我不知道如何克隆它。
这是第一个活动(我删除了一些不需要的功能):
public class TestActivity extends Activity implements OnClickListener
{
String ip;
int port;
Socket soc;
PrintWriter writer; // this works fine here
@Override
public void onCreate(Bundle savedInstanceState)
{
ip = "";
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Connect button click handler (you can skip this part)
Button connect = (Button)findViewById(R.id.connectBTN);
connect.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
EditText TB = (EditText)findViewById(R.id.ipTB);
ip = TB.getText().toString();
TB = (EditText)findViewById(R.id.portTB);
port = Integer.parseInt(TB.getText().toString());
try {
soc = new Socket(ip,port);
showDialog("Connected successfully!");
writer = new PrintWriter(soc.getOutputStream(), true);
}
catch(Exception er)
{
showDialog("Couldn't connect.\n"+er.getMessage());
soc = null;
}
}
} );
findViewById(R.id.controlmouseBTN).setOnClickListener(this);
// disconnect click handler (skip this part too)
Button disconnectBTN = (Button)findViewById(R.id.disconnectBTN);
disconnectBTN.setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
try
{
if(soc.isConnected()) soc.close();
writer.close();
}
catch(Exception er) { showDialog("Couldn't close connection.\n"+er.getMessage()); }
}
});
}
@Override
public void onClick(View v) // here is the erroneous part
{
//if(soc == null || !soc.isConnected()) { showDialog("Not connected to any computer."); return; }
//if(writer == null) return;
Intent i = new Intent(getApplicationContext(), PCController.class);
Intermediate inter = new Intermediate(); // this is the Parcelable class I've created
//inter.set(new String("hello")); (I tried sending a string, which worked fine, just to confirm that my Parcelable class is working)
inter.set(writer);
i.putExtra("printer", inter);
startActivity(i);
}
}
以下是Parcelable类Intermediate的代码
import android.os.*;
public class Intermediate implements Parcelable
{
Object ob;
public Intermediate()
{}
public Intermediate(Parcel parcel)
{
this.ob = parcel.readValue(Intermediate.class.getClassLoader());
}
public void set(Object o)
{ this.ob = o; }
public Object get()
{
return ob;
}
@Override
public int describeContents()
{ return 0; }
@Override
public void writeToParcel(Parcel dest, int flags)
{
dest.writeValue(this.ob);
}
// I don't understand this part though! Just copy pasted and modified the ClassName
public static final Intermediate.Creator<Intermediate> CREATOR = new Intermediate.Creator<Intermediate>() {
public Intermediate createFromParcel(Parcel in) {
return new Intermediate(in); }
public Intermediate[] newArray(int size) {
return new Intermediate[size]; }
};
}
这是被激活的下一个活动的代码。 (我只发布了必要部分)
PrintWriter writer;
String s; // for testing purpose
Swipe swipe; // a SurfaceView
public void onCreate(Bundle bundle)
{
super.onCreate(bundle);
swipe = new Swipe(this);
swipe.setOnTouchListener(this);
setContentView(swipe);
Intent i = getIntent();
Intermediate ob = (Intermediate)i.getParcelableExtra("printer");
writer = (PrintWriter)ob.get();
//s = (String)ob.get();
//showDialog(s); // this shows up the string I had sent, which means the string is getting passed.
}
现在当我没有连接(即writer
为空)并且我开始下一个Activity时,没有任何反应(没有错误)。
但是当我连接(writer
不为空)并且我开始下一个活动时,MAIN活动就会崩溃。我没有费心去记录错误信息,因为我知道我在这里做错了。
任何帮助将不胜感激!谢谢!
编辑:这是异常堆栈跟踪
10-26 00:37:55.445: WARN/System.err(251): java.lang.RuntimeException: Parcel: unable to marshal value java.io.PrintWriter@44eb0b40
10-26 00:37:55.474: WARN/System.err(251): at android.os.Parcel.writeValue(Parcel.java:1087)
10-26 00:37:55.484: WARN/System.err(251): at android.test.Intermediate.writeToParcel(Intermediate.java:33)
10-26 00:37:55.484: WARN/System.err(251): at android.os.Parcel.writeParcelable(Parcel.java:1106)
10-26 00:37:55.494: WARN/System.err(251): at android.os.Parcel.writeValue(Parcel.java:1029)
10-26 00:37:55.504: WARN/System.err(251): at android.os.Parcel.writeMapInternal(Parcel.java:469)
10-26 00:37:55.514: WARN/System.err(251): at android.os.Bundle.writeToParcel(Bundle.java:1445)
10-26 00:37:55.524: WARN/System.err(251): at android.os.Parcel.writeBundle(Parcel.java:483)
10-26 00:37:55.534: WARN/System.err(251): at android.content.Intent.writeToParcel(Intent.java:5237)
10-26 00:37:55.544: WARN/System.err(251): at android.app.ActivityManagerProxy.startActivity(ActivityManagerNative.java:1204)
10-26 00:37:55.554: WARN/System.err(251): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1373)
10-26 00:37:55.564: WARN/System.err(251): at android.app.Activity.startActivityForResult(Activity.java:2749)
10-26 00:37:55.574: WARN/System.err(251): at android.app.Activity.startActivity(Activity.java:2855)
10-26 00:37:55.584: WARN/System.err(251): at android.test.TestActivity.onClick(TestActivity.java:80)
10-26 00:37:55.594: WARN/System.err(251): at android.view.View.performClick(View.java:2364)
10-26 00:37:55.606: WARN/System.err(251): at android.view.View.onTouchEvent(View.java:4179)
10-26 00:37:55.615: WARN/System.err(251): at android.widget.TextView.onTouchEvent(TextView.java:6541)
10-26 00:37:55.624: WARN/System.err(251): at android.view.View.dispatchTouchEvent(View.java:3709)
10-26 00:37:55.634: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:37:55.634: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:37:55.644: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:37:55.656: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:37:55.664: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
10-26 00:37:55.674: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
10-26 00:37:55.684: WARN/System.err(251): at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
10-26 00:37:55.694: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
10-26 00:37:55.705: WARN/System.err(251): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
10-26 00:37:55.714: WARN/System.err(251): at android.os.Handler.dispatchMessage(Handler.java:99)
10-26 00:37:55.724: WARN/System.err(251): at android.os.Looper.loop(Looper.java:123)
10-26 00:37:55.734: WARN/System.err(251): at android.app.ActivityThread.main(ActivityThread.java:4363)
10-26 00:37:55.744: WARN/System.err(251): at java.lang.reflect.Method.invokeNative(Native Method)
10-26 00:37:55.754: WARN/System.err(251): at java.lang.reflect.Method.invoke(Method.java:521)
10-26 00:37:55.764: WARN/System.err(251): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-26 00:37:55.774: WARN/System.err(251): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-26 00:37:55.785: WARN/System.err(251): at dalvik.system.NativeStart.main(Native Method)
10-26 00:38:02.424: WARN/System.err(251): java.lang.RuntimeException: Parcel: unable to marshal value java.io.PrintWriter@44eb0b40
10-26 00:38:02.454: WARN/System.err(251): at android.os.Parcel.writeValue(Parcel.java:1087)
10-26 00:38:02.454: WARN/System.err(251): at android.test.Intermediate.writeToParcel(Intermediate.java:33)
10-26 00:38:02.464: WARN/System.err(251): at android.os.Parcel.writeParcelable(Parcel.java:1106)
10-26 00:38:02.474: WARN/System.err(251): at android.os.Parcel.writeValue(Parcel.java:1029)
10-26 00:38:02.486: WARN/System.err(251): at android.os.Parcel.writeMapInternal(Parcel.java:469)
10-26 00:38:02.494: WARN/System.err(251): at android.os.Bundle.writeToParcel(Bundle.java:1445)
10-26 00:38:02.505: WARN/System.err(251): at android.os.Parcel.writeBundle(Parcel.java:483)
10-26 00:38:02.514: WARN/System.err(251): at android.content.Intent.writeToParcel(Intent.java:5237)
10-26 00:38:02.524: WARN/System.err(251): at android.app.ActivityManagerProxy.startActivity(ActivityManagerNative.java:1204)
10-26 00:38:02.534: WARN/System.err(251): at android.app.Instrumentation.execStartActivity(Instrumentation.java:1373)
10-26 00:38:02.544: WARN/System.err(251): at android.app.Activity.startActivityForResult(Activity.java:2749)
10-26 00:38:02.554: WARN/System.err(251): at android.app.Activity.startActivity(Activity.java:2855)
10-26 00:38:02.554: WARN/System.err(251): at android.test.TestActivity.onClick(TestActivity.java:80)
10-26 00:38:02.564: WARN/System.err(251): at android.view.View.performClick(View.java:2364)
10-26 00:38:02.574: WARN/System.err(251): at android.view.View.onTouchEvent(View.java:4179)
10-26 00:38:02.584: WARN/System.err(251): at android.widget.TextView.onTouchEvent(TextView.java:6541)
10-26 00:38:02.594: WARN/System.err(251): at android.view.View.dispatchTouchEvent(View.java:3709)
10-26 00:38:02.604: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:38:02.614: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:38:02.625: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:38:02.634: WARN/System.err(251): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
10-26 00:38:02.644: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1659)
10-26 00:38:02.654: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1107)
10-26 00:38:02.664: WARN/System.err(251): at android.app.Activity.dispatchTouchEvent(Activity.java:2061)
10-26 00:38:02.674: WARN/System.err(251): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1643)
10-26 00:38:02.684: WARN/System.err(251): at android.view.ViewRoot.handleMessage(ViewRoot.java:1691)
10-26 00:38:02.694: WARN/System.err(251): at android.os.Handler.dispatchMessage(Handler.java:99)
10-26 00:38:02.704: WARN/System.err(251): at android.os.Looper.loop(Looper.java:123)
10-26 00:38:02.714: WARN/System.err(251): at android.app.ActivityThread.main(ActivityThread.java:4363)
10-26 00:38:02.714: WARN/System.err(251): at java.lang.reflect.Method.invokeNative(Native Method)
10-26 00:38:02.724: WARN/System.err(251): at java.lang.reflect.Method.invoke(Method.java:521)
10-26 00:38:02.734: WARN/System.err(251): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-26 00:38:02.744: WARN/System.err(251): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-26 00:38:02.754: WARN/System.err(251): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分:3)
你在这里遇到了更大的问题。你不应该使用Parcels在活动之间传递东西。根据android文档:
Parcel不是通用序列化机制。此类(以及用于将任意对象放入包中的相应Parcelable API)被设计为高性能IPC传输。因此,将任何Parcel数据放入持久存储中是不合适的:Parcel中任何数据的底层实现的更改都可能导致旧数据不可读。
您应该使用捆绑包。我通常做的是在类中创建两个静态方法,我试图在名为toBundle和fromBundle的活动之间传递。 toBundle接受我想要传输的类的实例并返回一个包。 fromBunle接受一个包并返回该类的实例。
我不知道在Activities之间传递像PrintWriter这样的复杂对象的方法。但是你的代码也存在其他问题。你在主UI线程上做网络的东西。这将导致您的应用程序冻结很多。您需要将所有IO移至另一个线程。这很好,因为那样你就可以将所有IO内容移动到一个可以从两个活动中访问的单独类中。例如,使用IntentService。这将使你的应用程序sooooooo更好。您可能还想阅读文章Painless Threading。这是我推荐给所有Android开发人员的关键读物。
答案 1 :(得分:0)
您无法使用任何常规Android数据传递方法(Bundles / Parcels)在两个Android活动之间传递PrintWriter。如果必须在两个活动之间共享PrintWriter,则可以使用静态变量。
话虽这么说,您也可以编写一个您在每个Activity上访问和使用的服务。您可能需要查看ApiDemos项目中的LocalService示例,以获取有关如何执行此操作的示例。关于这一点,网上也有无数的教程。